<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
</head>
<body>
<script>
    var txt = "欢迎光临";
    console.log(typeof txt);
    var num = 10;
    var num1 = "10";
    console.log(typeof num1);
    console.log(typeof String(num));
</script>
</body>
</html>